Two rockets were fired into northern Israel from Lebanon on Friday, and Israel's army responded with artillery fire, Lebanon's news agency and security sources said.

The attacks came as Israel continued to carry out air strikes on targets in the Gaza Strip, and Hamas militants fired more rockets into Israel from the southern coastal enclave.

Lebanon's news agency NNA said the rockets were fired towards "occupied territories" at 6:30 am local time from the Hasbaya area in Lebanon.

Israel's chief military spokesman, Brigadier-General Moti Almoz, said one rocket fell near Kibbutz Kfar Yuval, a farming community, with no casualties or damage.

According to Lebanese security sources, there were five rockets fired in total from southern Lebanon.

Two rockets entered Israel, one fell into Lebanese territory and two more were intercepted.

Southern Lebanon is a stronghold of Hezbollah, a Shiite Muslim group that battled Israel seven years ago and is engaged in Syria's civil war in support of president Bashar al-Assad, but Palestinian groups are also present in the area.

There have been several exchanges across the border in the past year.

In December, rockets launched from Lebanon struck northern Israel provoking a response across the border that had been largely quiet since a war in 2006.

In August, Brigades of Abdullah Azzam, an organisation linked to Al Qaeda, claimed a rocket barrage from Lebanon.

Palestinian militants in the Gaza Strip have launched hundreds of rockets into Israel this week.

Israel has responded with attacks which have killed nearly 80 Palestinians so far.

Israel continued that offensive on Friday, striking the Hamas-dominated enclave from air and sea.

Palestinian authorities say most of the dead are civilians. Israel says its attacks are targeted against militants and are aimed at ending persistent rocket attacks on its civilian population.

Local emergency services in the Israeli port city of Ashdod said a rocket hit a petrol station, causing a fire and wounding at least three people.

The salvoes into Israel have caused no fatalities due in part to interceptions by Israel's partly-US-funded Iron Dome aerial defence system.

Israeli leaders hint at ground invasion

Israeli leaders have appeared to hint at a possible invasion by ground forces and some 20,000 army reservists have been mobilised giving them the means, if they choose, to mount a land offensive.

The Israeli military says more than 470 projectiles have been fired at Israel since Tuesday by Hamas and by other militant groups.

Some rockets have landed more than 100 kilometres from Gaza.

Sirens sounded as far north as the Israeli city of Haifa on Friday though police said no remnants of rockets, which Hamas said it had fired, were found.

Medical officials in Gaza said at least 60 civilians, including a four-year-old girl and a five-year-old-boy killed on Thursday, were among the 79 Palestinians who have died since the offensive began on Tuesday.

US president Barack Obama told Israeli prime minister Benjamin Netanyahu by telephone on Thursday that the United States was willing to help negotiate a ceasefire.

Mr Netanyahu said in a televised statement on Thursday that: ""So far the battle is progressing as planned, but we can expect further stages in future. Up to now, we have hit Hamas and the terror organisations hard and as the battle continues we will increase strikes at them."

Mr Netanyahu discussed options with his security cabinet.

The last time Israel launched a ground offensive against Gaza was in early 2009.

Ground troops did not cross into the Gaza Strip during the last major exchange of rockets and missiles in October 2012.

"We have long days of fighting ahead of us," Israeli defence minister Moshe Yaalon said.

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